This invention relates to the fields of dielectrokinesis (phoresis), dielectric relaxation dynamics, electronic devices and systems and, more particularly, to a selective polarization matching filter for triggering and maximizing the dielectrokinesis response in the detection of specific entities consisting of organic and inorganic materials via detection of a force or replenishment energy density of stored electrical energy.
The detection of the presence or absence of specific entities--human beings, plastics (mixtures of various polymers and with additives) and other organic/inorganic materials--irrespective of the presence of intervening vision-obstructing structures or EMI signals has uses in very diverse applications such as: (a) fire fighting and rescue; (b) national border security; (c) transportation security in pre-boarding planes, trains and automobiles; (d) new and old construction industry; (e) law enforcement; (f) military operations; (g) anti-shoplifting protection; (h) other security and emergency needs and operations, etc.
It is known that humans, animals and other animate species generate an external electric field and gradients thereof. For example, in human physiology, the central and peripheral nervous system neurons, the sensory system cells, the skeletal muscular system, as well as the cardiac conduction cells and cardiac muscle system cells all operate by a depolarization and repolarization phenomena occurring across their respective cellular membranes, which are naturally in a dielectric polarization state.
The trans-membrane ion currents and potentials utilizing Na.sup.+1, K.sup.+1 ions, etc., all work to establish a resting potential across the cell membranes that can be characterized as a high state of polarization. The ion concentration (moles/cm.sup.3) within and surrounding the unmyelinated cell axon establish the resting potential. The fluids themselves are neutral. What keeps the ions on the membrane is their attraction for each other across the membrane. Independent of this process the Cl.sup.-1 ions tend to diffuse into the cell since their concentration outside is higher. Both the K.sup.+1 and Cl.sup.-1 diffusion tend to charge the interior of the cell negatively and the exterior of the cell positively. As charge accumulates on the membrane surface, it becomes increasingly difficult for more ions to diffuse. K.sup.+1 ions trying to move outward are repelled by the positive charge already present. Equilibrium is reached when the tendency to diffuse because of the concentration is balanced by the electrical potential difference across the membrane. The greater the concentration difference, the greater the potential difference across the membrane. The resting potential can be calculated by the Nernst Equation, wherein the potential (V)=V.sub.Inside -V.sub.Outside such that: ##EQU1## where Co and Ci are ion concentrations inside and outside, k is the Boltzmann constant, T is absolute temperature, e is the charge on the electron and z is the valence (number of electron charges) on the ion.
The nerve and conduction impulses, as well as the sensory, cardiac, and muscular action potentials and subsequent responses are manifested via sequential periodic pulses (waves) resulting in first rapid depolarization and, shortly after, rapid repolarization to reestablish the rest state, namely, the original polarization state of the membrane. The transverse membrane ion currents produce a dipole charge that moves along the cell membrane. The greater the stimulus the more the pulses that are produced along the membrane.
The action potentials are related to the ratio of the respective ion concentrations inside and outside the different types of membranes. The resultant polarization electrical field distribution pattern has a high degree of spatial non-uniformity and can be characterized as a bound dipolar charge distribution pattern. A detailed discussion of the human generated electric field can be found in R. A. Rhodes, Human Physiology, Harcourt Brace Javanovich (1992) and D. C. Gianocoli, Physics Principles with Applications, Prentice Hall (1980), the teachings of which are hereby incorporated by reference.
Alternatively, the external electric field and gradients thereof can be supplied by an external source via static electrification for use with inanimate targets such as plastics, metals, water, etc.
It would be advantageous to be able to detect the external electric field and gradients thereof, either generated naturally by an animate species or induced by an external source, on an entity specific basis. It would further be advantageous to enable this detection at great distances and through obstructions. It has been discovered that such detection is possible using the selective polarization matching filter in accordance with the present invention in conjunction with the principles of dielectrophoresis.
Dielectrophoresis describes the force upon and mechanical behavior of initially neutral matter that is dielectric polarization charged via induction by external spatially non-uniformity electric fields. The severity of the spatial non-uniformity of the electric field is measured by the spatial gradient (spatial rate of change) of the electric field. A fundamental operating principle of the dielectrophoresis effect is that the force (or torque) in air generated at a point and space in time always points (or seeks to point) in the same direction, mainly toward the maximum gradient (non-uniformity) of the local electric field, independent of sign (+ or -) and time variations (DC or AC) of electrical fields (voltages) and of the surrounding medium dielectric properties.
The dielectrophoresis force magnitude depends distinctively nonlinearly upon the dielectric polarizibility of the surrounding medium, the dielectric polarizibility of initially neutral matter and nonlinearly upon the neutral matter's geometry. This dependance is via the Clausius-Mossotti function, well-known from polarizibility studies in solid state physics. The dielectrophoresis force depends nonlinearly upon the local applied electric field produced by the target. The dielectrophoresis force depends upon the spatial gradient of the square (second power) of the target's local electric field distribution at a point in space and time where a detector is located. The spatial gradient of the square of the local electric field is measured by the dielectrophoresis force produced by the induced polarization charge on the detector. This constant-direction-seeking force is highly variable in magnitude both as a function of angular position (at fixed radial distance from the target) and as a function of the radial position (at a fixed angular position) and as a function of the "effective" medium polarizibility. The force's detection signature is a unique pattern of the target's spatial gradient of the local electric field squared, with the detector always pointing (seeking to point) out the direction of the local maximum of the gradient pattern. All experimental results and equations of dielectrophoresis are consistent with the fundamental electromagnetic laws (Maxwell's equations).
There are five known modes of dielectric polarization. These include: electronic polarization, where electron distribution about the atom nuclei is slightly distorted due to the imposed external electric field; atomic polarization, where the atom's distribution within initially neutral matter is slightly distorted due to the imposed external electric field; nomadic polarization, where in very specific polymers, etc., highly delocalized electron or proton distribution is highly distorted over several molecular repeat units due to the imposed external electric field; rotational polarization (dipolar and orientational), where permanent dipoles (H.sub.2 O, NO, HF) and orientable pendant polar groups (--OH, --Cl, --CN, --NO.sub.2) hung flexibly on molecules in material are rotationally aligned toward the external electric field with characteristic time constants; and interfacial (space charge) polarization, where inhomogeneous dielectric interfaces accumulate charge carriers due to differing small electrical conductivities. With the interfacial polarization, the resulting space charge accumulated to neutralize the interface charges distorts the external electric field with characteristic time constants.
The first three modes of dielectric polarization, electronic, atomic and nomadic, are molecular in distance scale and occur "instantaneously" as soon as the external electric field is imposed and contribute to the dielectric constant of the material at very high frequencies (infrared and optical). The last two polarization modes, rotational and interfacial, are molecular and macroscopic in distance scale and appear dynamically over time with characteristic time constants to change (usually increase) the high frequency dielectric response constant toward the dielectric constant at zero frequency. These characteristic material time constants control the dielectric and mechanical response of a material.
The modes of polarization and their dynamics in contributing to the time evolution of dielectric constants are discussed in various publications, such as H. A. Pohl, Dielectrophoresis, Cambridge University Press (1978); R. Schiller Electrons in Dielectric Media, C. Ferradini, J. Gerin (eds.), CRC Press (1991), and R. Schiller, Macroscopic Friction and Dielectric Relaxation, IEEE Transactions on Electrical Insulation, 24, 199 (1989), the well-known teachings of which are hereby incorporated by reference.